The present invention is related to the invention disclosed in U.S. Pat. No. 5,223,126, issued Jun. 29, 1993, the specification of which is incorporated by reference.
In the typical dry cleaning process, a small amount of dry cleaning waste water is formed, generally consisting of a mixture of water and a dry cleaning solvent. The waste water also contains solid particulate matter, such as dirt or lint, which is often suspended in the mixture. Perchloroethylene is the most common dry cleaning solvent in commercial use today.
Traditionally, this waste water mixture was merely disposed of. However, it has become increasingly important that the water and solvent be separated, both for economic and environmental reasons. By reclaiming the solvent from the waste water, the solvent can be re-used in the dry cleaning process, thereby reducing the operational cost of a dry cleaning establishment. Moreover, environmental considerations require that none of the solvent be released into the environment and often prohibit the release of waste water into sewer systems, even after the solvent has been removed.
A number of systems for reclaiming solvent from dry cleaning waste water have been proposed. For example, U.S. Pat. No. 4,637,232 to Zucchini discloses a distillation apparatus which separates the waste water solvent and water components. A distillation chamber vaporizes the azeotropic mixture of solvent and water, and produces a fluid which condenses to pure solvent that may be drawn away for use in the dry cleaning process. The Zucchini apparatus suffers from a number of shortcomings. First, the azeotropic mixture is highly corrosive due to the formation of hydrochloric (HCl) acid from the chloride solvent and water. Such acidity is especially damaging to metallic components of the apparatus. Although Zucchini attempts to control this by keeping the mixture predominantly solvent, even trace amounts of HCl can damage the distillation chamber and tank. Second, because solvent continues to remain in the mixture with water, the water cannot be safely disposed of. Third, even if all of the solvent was removed from the water, the Zucchini system would run afoul of regulations, so-called "sunset rules", which prohibit the release of previously contaminated water into the environment.
U.S. Pat. Nos. 4,513,590 to Fine and 4,354,364 to Holder et al. also disclose systems which can remove solvent from a waste water mixture. However, neither reference provides an apparatus which can purify the water from the waste water mixture.
The invention disclosed in U.S. Pat. No. 5,223,126 (the '126 system) solved many of the aforementioned problems associated with the Zucchini, Fine and Holder et al. systems by providing a system which removes essentially all of the solvent from the dry cleaning waste water mixture. However, the '126 system boiled the decontaminated waste water and vented the resulting steam into the atmosphere. As noted above, "sunset rules" may prohibit such venting.
Accordingly, a need exists for an apparatus which decontaminates the dry cleaning waste water mixture, resulting in pure solvent and pure water, both of which are recycled back into the dry cleaning system without exposing the environment to either.